1. Field of the Invention
The present invention relates to a glass fiber package in which a glass fiber aggregate which contains an alkali-containing glass wool fiber containing 5% or more by weight or, particularly, 10% or more by weight of alkali metal oxide components having a finely small diameter of an average fiber diameter of not larger than 5 μm or, particularly, smaller than 1 μm which is able to be advantageously used as a main material of, for example, a filter paper or a separator for a lead-acid battery is packed in a compressed state so as to give a form which is able to be handled as a freight; to a method for packing of glass fiber; and also to a glass fiber product using the same.
2. Description of the Related Art
Up to now, an alkali-containing glass wool fiber of a fine diameter where an average fiber size is 5 μm or less containing 5% or more by weight or, particularly, 10% or more by weight of alkali metal oxide components so as to impart a resistance to acid being able to be durable against a sulfuric acid electrolysis solution has been used as a main material for a separator for a lead-acid battery. Particularly in the case of a separator for a valve regulated lead-acid battery, it is necessary that the electrolysis solution is kept in a separator and, therefore, very fine glass fiber where an average fiber size is less than 1 μm has been used (the fiber where an average fiber size is up to about 0.5 μm has been practically used).
In such an alkali-containing glass wool fiber where an average fiber size is 5 μm or less or even smaller than 1 μm, a wool fiber which is made into fiber and manufactured by a method such as a flame attenuation process (a method where fused glass is flown in a yarn shape from the nozzles at the bottom of a fusing furnace and blown away with a high-speed flame) or a centrifugal process (rotary process or rotary fiberization process; a method where fused glass is provided to a cylindrical container where many orifices are bored at the surrounding wall called spinner being rotated at high speed, spun by centrifugal force and blown away by a high-speed steam) forms a fiber aggregate and, taking the packing efficiency upon transportation (volume reducing rate) into consideration, it is packed in a compressed state and handled.
Since the above glass fiber has a fine fiber size and a poor elasticity, there have been frequent problems that, when it is packed in a compressed state and is handled, the fiber length becomes short due to breakage such as bending of the fiber and the properties inherent to the glass fiber material available immediately after the manufacture of the glass fiber are unable to be achieved. When the fiber size is fine, such an influence is significant.
For example, in the above-mentioned separator for a valve regulated lead-acid battery, it is usually prepared by subjecting only the above glass fiber where an average fiber size is smaller than 1 μm to a wet paper manufacturing to form a sheet where the basis weight is not more than about 170 g/m2 and, since it is necessary to ensure a predetermined tensile strength substantially by the entangling action of the glass fiber only, there is an inconvenience that, when the fiber length of the glass fiber material is short, an operation of making into a sheet itself is not possible or tensile strength after making into a sheet is insufficient. Further, since the above-mentioned separator for a valve regulated lead-acid battery is used in such a manner that, usually, a separator is bent into a U shape so as to enclose any of positive and negative plates therein whereby it is installed between positive and negative plates, there is an inconvenience that, when the fiber length of the glass fiber material becomes short, cracks are apt to be resulted at the bent part of the separator. Incidentally, as to a yardstick for estimating the degree of changes in the glass fiber length in the above glass fiber paper sheet through wet paper making process, elongation of said sheet is to be measured. In recent years, a product where a wet paper manufacturing is conducted using the above glass fiber having less than 1 μm of an average fiber size as a main material to form into a sheet having a basis weight of not more than about 30 g/m2 has been used as a separator for electric double layer capacitors.
Since glass fiber has a high affinity to water (angle of contact is 0°) and its very fine fiber has a big specific surface area, the above glass fiber material adsorbs water in the air during the storage period, etc. from the stage of being made into fiber and manufactured until the stage of being used as a separator for a lead-acid battery, etc. Although its degree varies depending upon fiber size, packing state, storage environment, etc., the fiber surface usually adsorbs water in an amount of about 0.5 to 1.0% by weight in the case of the above glass fiber where an average fiber size is smaller than 1 μm. When much amount of water is adsorbed with the surface of the glass fiber, there happens a phenomenon that alkali metal oxide components (such as Na2O, K2O and Li2O3) in the glass fiber are eluted and glass fibers are adhered each other. When the glass fibers are adhered each other, the fiber size becomes large and there is resulted an inconvenience that the properties inherent to the glass fiber material which are available immediately after the manufacture of glass fiber are no longer achieved. Such an adhesion phenomenon has been found to be affected not only by glass fiber size, alkali metal oxide amount of the glass fiber, storing period, storing environment, etc., but also by packing density (degree of compression) in the compression packing. Thus, it has been found that, although the above eluting phenomenon of the alkali metal oxide components is resulted principally independently of the packing density, the adhesion phenomenon is resulted being caused by the above eluting phenomenon at the places where the glass fibers are contacted each other and, when the packing density (degree of compression) is higher, the contacting places and contacting areas of the glass fibers increase whereby the above adhesion phenomenon is apt to happen.